The music department orders 4 times as many Rock CDs as Jazz CDs. If the department orders 550. CDs, how many of CDs are rock?

440 Rock CDs

Step-by-step explanation:

Let number of rock CDs be "r", and

number of Jazz CDs be "j"

4 times as many Rock as Jazz, so we can write:

r = 4j

Total of 550 CDs, thus we can write equation 2:

r + j = 550

Now we replace 2nd equation with 1st equation and find j first:

r + j = 550

4j + j = 550

5j = 550

j = 550/5

j = 110

Now, finding r:

r = 4j

r = 4 (110)

r = 440

There are 110 Jazz CDs and 440 Rock CDs